Hundreds, if not thousands, of fish call the interior of this former oil rig, known as the High Island 389, home. The rig, technically a production platform, may one day be part of the Rigs to Reefs program, which converts decommissioned oil rigs into artificial reefs.
Daniel Terdiman/CNET

FLOWER GARDEN BANKS, GULF OF MEXICO -- The warning was clear: Go anywhere you want inside the long, long legs of the oil rig, but stick your head outside the perimeter of the platform and you risk getting brained by tools plummeting from above.

Far below the rig, known as High Island 389, it was a marine paradise. Everywhere you looked, barracuda, spadefish, gray triggerfish, Spanish hogfish, and much more marine life swam in abundance. A few sharks lurked farther down. And then, of course, there were the scuba divers -- short-term visitors to this watery sanctuary.

Welcome to the Rigs to Reefs program, an initiative kick-started by the US Congress in 1984, and then rolled out across the Gulf states -- Texas, Mississippi, Louisiana, Alabama, and Florida -- in the years after that. To date, about 450 former oil rigs -- technically known as production platforms -- have been transformed from functioning petrochemical platforms to permanent artificial reefs in the Gulf. The Coastal Marine Institute estimates that each one of these giant structures can make a two- to three-acre home for hundreds of marine species, and a population of between 12,000 and 14,000 fish.

As part of CNET Road Trip 2014, I've traveled more than 100 miles into the Gulf from the small coastal town of Freeport, Texas, aboard a charter boat known as the Fling to scuba dive a huge national marine sanctuary known as the Flower Garden Banks. Now we're about to go more than 80 feet below the surface to see the vibrant scene inside the seemingly endless structure of a rig.

Don't tow away

Many times, when a Gulf of Mexico oil rig ends its service, it is simply towed back to shore, broken up, and that's the end of the story. But according to Dale Shively, the leader of the artificial reef program at the Texas Department of Parks and Wildlife, there was a concern in the late 1980s that as these huge structures were removed, so too was the marine habitat that had grown up around it over the previous 30 or so years.

That was the impetus behind creating the Gulf-wide Rigs to Reefs program. In 1990, the Texas legislature formalized that state's artificial reef program, creating a process for working with oil companies to maintain the rig-based habitats, either in place, or in newly designated areas at sea.

The government mandate was clear -- the program had to be self-sufficient. So a clever system was worked out: Participating oil companies willing to donate their ex-rigs would give the program half the money they would save by not having to pay to tow the rigs all the way to shore. Depending on the size of the rig, and how far from shore it is, that can amount to millions of dollars, or it can be zero. But on average, Shively said, the Texas artificial reef program gets about $250,000 per platform.

As of today, Shively said, Texas has collected 140 platforms that are located at about 50 Rigs to Reef sites. Each of those sites comprises about 40 total acres of Gulf real estate, an amount of space that provides plenty of room for expansion. Some sites may have just one platform, while others have up to 10, Shively said. "You try to cluster materials together," he added, "to try to simulate a more natural type reef."

How the reefs are made

According to the US Bureau of Safety and Environmental Enforcement (BSEE), there are three methods for converting a former rig into a reef, with the well first being capped in each case. The first is known as "tow and place," and "involves severing the structure from the sea floor, either using explosives or mechanical cutting techniques, and then towing it to the selected reef for deployment."

More adventures from Road Trip 2014

Check out the latest from Daniel's trip to the best tech spots in Texas, Oklahoma, Kansas, and more.

The second method is called "topple in place," which means detaching the "structure from the seabed [and toppling it] onto its side." Finally, there's "partial removal," in which the top section of the rig is "severed at a permitted navigational depth, typically 85 feet deep, and placed on the sea floor next to the base of the remaining structure."

Not every former rig can be converted. According to BSEE, factors such as platform size, structural integrity, complexity, and location are used to determine whether a rig qualifies. "Complex, stable, durable, and clean platforms are generally candidates for reefing," the BSEE wrote on its Web site. "Platforms toppled due to structural failure are not candidates."

Shively said that though the top of a converted rig typically ends about 85 feet below the surface, there are times when there's just 50 feet of clearance. In those cases, crews must install a navigational buoy. But if the 85 foot clearance level is possible, no buoy is required.

In the areas near the Flower Garden Banks, he added, the sea floor tends to be about 200 feet below the surface. At High Island 389, the depth is about 300 feet. But in some areas, the floor can go down to 600 or even 700 feet.

As a scuba diver, especially one with scant experience, it's crucial not to go below about 130 feet. Yet inside the structure of a rig like 389, it's utterly tempting to follow fish much further down. Add that to the list of dangers that include getting hit by falling tools. The trick, I quickly learned, was to be happy moving slowly in a small area, at suitable depth, and letting the fish come to me. With thousands of them swarming the area, that was not a problem.

High Island 389

At High Island 389, an eight-leg production platform that descends 300 feet below the surface, oil recovery has been halted for years. But we're told as we prepare to jump into the water to dive it, there's still a skeleton crew aboard, and from time to time, they've been known to drop tools over the edge. Getting cracked in the skull by a hammer while 100 feet down would not be a good thing, so we need to stay within the perimeter of the platform while diving.

As we enter the water, there's little to see. The bottom is too far below, and if there are any fish nearby, they're not showing themselves. But as we pull ourselves down a safety line tied to one of the platform's giant legs, the teeming marine life inside the perimeter overwhelms our view. Over the course of two days aboard the Fling, we'd dove a number of Flower Garden sites, but this artificial reef had by far the most marine life.

The High Island 389, seen from the surface of the Gulf of Mexico.
Daniel Terdiman/CNET

That's exactly the point, Shively explained. Fish love the rigs because they provide what he called "hard substrate" -- stable, durable, and complex fixtures that rise from the sea bottom, providing sanctuary for small species, and plenty of room for larger species to move around. "They have their own little mini-ecosystems associated with each rig," Shively said, in a sea that, beyond the fish-favorite Flower Garden Banks, is otherwise largely flat and featureless on the bottom.

It's not entirely understood where the fish came from, but Shively said that the basic idea is that long ago, they followed currents and found the rig structures, slowly establishing home bases there. If a decommissioned rig is fully removed, those ecosystems are destroyed. But "when you reef in place, you already have marine life growing" there, he said. As a scuba diver, that's a very big attraction.

As Shively puts it, "the main benefit of [Rigs to Reefs] is the preservation of marine habitat, and with that, you also have the social aspects of adding more fishing and diving opportunities."

Before and after

Sitting in the wheelhouse of the Fling, Captain Bland Ellen steered the boat across the Gulf waters. A longtime firefighter and police officer, among other emergency-services jobs, Ellen, sporting a white goatee and an easy smile, recalled how he had retired in his early 40s, and unexpectedly become a boat captain.

A scuba expert with tons of experience at some of the world's best dive sites, he'd reluctantly taken a trip to the Flower Garden Banks in 1999, expecting to be bored. But the vibrant life of the marine sanctuary hooked him, and before long, he was helming the Fling, the only commercial boat that makes trips to the area.

The Fling has an exclusive contract with the Texas Department of Parks and Wildlife to monitor the converted rigs, Ellen said, his eyes scanning the sea's horizon for danger. Once a month, the boat brings a crew of researchers from the Rigs to Reef program, Texas A&M University, and the US Geological Survey to both check existing reefed sites and look into new sites that will soon be part of the program. The idea is to get a before-and-after look at the environment, in particular a baseline of the quantity of species at the sites, as well as the sizes of different fish.

This barracuda is just one of thousands of fish that call the interior of the High Island 389 home.
Daniel Terdiman/CNET

As is evident from my reaction, and that of my fellow divers, the chance to see the life 100 feet below the surface at High Island 389 is one of the main attractions of the trip to the Flower Garden Banks. Ellen explained that the Fling has an agreement with W&T Offshore -- the rig's owner -- that allows for our excursion there.

Neither Shively nor Ellen are certain what will become of 389, which Ellen said had been shut down as an operational rig after being damaged during 2008's Hurricane Ike, in all likelihood because the cost of fixing the platform was determined to be higher than the value of its continued oil production. The hope is that W&T will donate 389 to Rigs to Reefs. According to W&T, that plan is under consideration, but no final determination has yet been made. As of now, 389 is officially "idle," the company said.

Public outreach

One of the odd things about the Flower Garden Banks is that, despite its ample beauty, and proximity to easy-to-access ports, few people, even divers, know about it. That's something Ellen hopes the trips like mine on the Fling can help remedy, especially because he's noticed people's attitudes toward the Gulf of Mexico change after the trip. "Maybe they'll think a little bit before they pour that oil down the drain or drop that plastic bag," he said, "after they see all those turtles and fish."

The Rigs to Reefs program has the same problem. Shively said the program's leaders have done a number of things to build awareness, but a recent survey by Texas A&M showed that most people, even in Texas, don't know about the initiative. "We're scratching our heads," he said, "trying to figure out how to get the word out."

Back at the helm of the Fling, Ellen has the same feeling about the program. He said that anyone can fish or dive the many artificial reef sites, once they're in the loop. "You have to be pretty skilled and well equipped to find them and tie into them," Ellen said. "In fact, most people don't even know they exist out here."